The traditional process for paving roadways with asphalt paving material is generally carried out by an asphalt paving machine and a number of supply trucks which transport the asphalt paving material from an asphalt production plant to the paving machine. The paving machine generally is self-propelled and driven by a wheeled or tracked drive system. A hopper is located at the front end of the machine to receive asphalt paving material from a dump-type supply truck, and a floating screed is located at the rear end of the machine to form the asphalt mat. A conveyor delivers the asphalt paving material from the hopper to the road base just ahead of the screed, where a distributing auger distributes the asphalt paving material across the roadway in front of the screed.
In recent years, material transfer vehicles have been frequently used to shuttle asphalt paving material between the supply trucks and the paving machine. A self-propelled material transfer vehicle typically includes a large-capacity truck-receiving hopper and an inclined truck-unloading conveyor extending upwardly from this hopper. Asphalt paving material is dumped from a supply truck into the truck-receiving hopper. Thereafter, it is carried upwardly by the truck-unloading conveyor from the truck-receiving hopper and discharged off the elevated output end of the truck-unloading conveyor into a chute mounted on the lower end of a paver-loading conveyor, or into an intermediate surge hopper that is sized to hold the entire load of a delivery truck. The discharge of asphalt material off the elevated output end of the truck-unloading conveyor so that it may fall under the influence of gravity into a chute or surge hopper assists in preventing undesirable segregation of the various particulate components of the asphalt paving material by particle size.
Material transfer vehicles of the type that are equipped with a surge hopper typically include a conveyor in the surge hopper that is adapted to transfer the asphalt paving material to a paver-loading conveyor. Paver-loading conveyors mounted on material transfer vehicles with and without surge hoppers are generally pivotable about an essentially vertical axis so that the transfer vehicle can be positioned alongside an asphalt paving machine that is laying an asphalt mat and rapidly discharge asphalt paving material into the hopper of the paving machine as the material transfer vehicle moves with the paving machine along the roadway. Because of its rapid loading and unloading capabilities, a material transfer vehicle can rapidly shuttle between delivery trucks at a pick-up point and an asphalt paving machine that is laying an asphalt mat at a paving site so that there is less likelihood that the paving machine will have to stop paving because of a lack of asphalt paving material.
A material transfer vehicle is operated by an operator in an operator's station that is located high enough to allow for unobstructed viewing of the roadway and the loading of the truck-receiving hopper. Conventionally, the operator's station is accessed by a vertical ladder located on the side or end of the operator's station. A stairway is easier and safer to use than a vertical ladder; however, a conventional stairway would occupy too much space and/or would protrude outside the periphery of the material transfer vehicle, thereby creating its own safety hazard. It would be advantageous if a stairway could be devised that would be located entirely within the periphery of the material transfer vehicle and would be easy and safe to use.